Automotive chassis-frame structures

ABSTRACT

Chassis-frame structure of automotive vehicle, notably of vehicle having a front power unit and transmission mechanism assembly, with driving front wheels connected through thrust links to the chassis frame, characterized in that it comprises a compound chassis consisting of an assembly of three main elements, that is, a front element constituted by a pair of lower parallel longitudinal members upswept at their front ends, and by a pair of upper longitudinal members each rigidly assembled at two junction nodes with one of said lower longitudinal members so as to double same along a portion corresponding to the cradle of the power unit, transmission and front-wheel assembly by means of an upswept curved portion having an outswept forward extension beyond said lower longitudinal members and their ends assembled by means of a curved horizontal cross member, said lower longitudinal members having rear extensions, the second element consisting of an intermediate chassis member in the form of a steel pressing formed in the conventional fashion with pressed reinforcing ribs and constituting the floor of the passengers&#39;&#39; compartment and comprising likewise pressed wells for the feet of the rear seat passengers, and finally a third or rear element consisting of a pair of parallel longitudinal members having a different relative spacing in comparison with said front longitudinal members.

States atent 5] Feb. 1, 1972 [54] AUTOMOTIVE CHASSIS-FRAME 3,520,5507/1970 Dysarz et a1. ..280/l06 STRUCTURES Primary Examiner-Kenneth H.Betts [72] Inventor: Michel Tuner, Billancourt, France Anomey stevens,Davis Ming. & MoshBr [73] Assignees: Regie Nationale Des Usines Renault,Billancourt; Automobiles Peugeot, Paris, France ABSTRACT 22 Filed; June15, 970 Chassis-frame structure of automotive vehicle, notably ofvehicle having a front power unit and transmission mechanism [21] APPL46035 assembly, with driving front wheels connected through thrust linksto the chassis frame, characterized in that it comprises a ForeignApplication Priority D t compound chassis consisting of an assembly ofthree main elements, that is, a front element constituted by a pair oflower July 22, 1969 France ..6924906 parallel longitudinal membersupswept at their from ends, and

- by a pair of upper longitudinal members each rigidly assem- [52] U.S.Cl. ..l/64 R, 180/93, 280/106, bled at v0 junction nodes with one ofSaid lower |ongitudina| 296/28 293/63 membels so as to double same alonga portion corresponding [51] Int. Cl. "B6261 21/00 to the cradle of thepower unit transmission and fronbwhecl [58] Field of Search ..296/28;lilo/64,42, 93, 82; assembiy by means of an upswept curved portionhaving an 280/106; 293/63 outswept forward extension beyond said lowerlongitudinal Referem Cited members and their ends assembled by means ofa curved horizontal cross member, said lower longitudinal members UNITEDSTATES PATENTS having rear extensions, the second element consisting ofan intermedlate chassis member in the form of a steel pressing 2,485,50010/1949 Lyman ..280/ 106 for ed in the onventional fashion with pressedreinforcing 2, 3, 2 6/ 958 F lts t al- ."/106 ribs and constituting thefloor of the passengets compartment 2,851,302 1953 w n x and comprisinglikewise pressed wells for the feet of the rear 3 1959 230/106 X seatpassengers, and finally a third or rear element consisting 3,022,8462/1962 Thompson "280/106 X of a pair of parallel longitudinal membershaving a different 3,073,647 1963 Benz "296/28 relative spacing incomparison with said front longitudinal 3,149,856 9/1964 Schiiberg.....296/28 X members 3,162,478 12/1964 Richards... ...280/106 X3,209,851 10/1965 Collins ..180/42 7 Claims, 5 Drawing Figures PATENTEDFEB 1 1 72 SHEET 1 OF 2 PATENTED FEB 1 2 sum 2 or 2 AUTOMOTIVECHASSIS-FRAME STRUCTURES The present invention relates to automotivevehicle chassisframe structures notably for front-engined vehicles withfront drive wheels, said structure constituting the under-frame orchassis of the vehicle.

Chassis-frame of motor vehicles, notably of passengers vehicles, musthave a good rigidity in order to withstand distortion stress applied tothe passengers compartment in case of crash and absorb vibrationgenerated by the power unit, on the one hand, and also the consequencesof ground unevennesses on the trains of wheels and the suspensionsystem, on the other hand.

Besides, these chassis-frames must be constructed as simply as possibleand have a minimum weight, for obvious reasons of cost and vehicleperformances.

Combining these contradictory requirements by using suitable meansconstitutes the essential object of this invention.

After the uniform design, used for many years, which consisted of achassis comprising a pair of longitudinal side members assembled by anumber of cross members, a rigid but heavy structure if any, automotivevehicles have been constructed according to the chassis-cum-bodytechnique whereby the inherent rigidity of the body is sufficient forimparting the necessary strength to the vehicle.

Pressed-steel floor chassis have also been constructed wherein thefunction of the ribbed and partly box-sectioned floor sheets constitutethe rigid basic structure of the vehicle.

However, self-supporting bodies, due to their greater structuralelasticity and their inherent vibration frequencies, do not ensure asatisfactory absorption of vibrations produced by the engine andtransmitted from the road surface through the suspension system;therefore, such chassis-cum-body constructions constitute a source ofvibratory resonance at certain speeds,

Conventional chassis comprising two longitudinal side members are usedonly in trucks or very large automotive vehicles, due to theirsubstantial weight and cost.

Pressed-steel or floor-type chassis are used chiefly in light cars orsmall delivery vans exposed only with limited structural stress. in thecase of larger vehicles, the necessity of reinforcing the floor platformmake this construction noncompetitive in comparison with otherstructures.

it is the essential object of the present invention to provide a framestructure constituting a combination of chassis elements with aconventional self-supporting or chassis-cum-body structure, as afunction of the points of action and reaction of the power unit andsuspension system of the vehicle.

This structure is characterized essentially in that it comprises acompound chassis consisting of an assembly of three main elements, thatis a front element constituted by a pair of lower parallel longitudinalmembers upswept at their front ends, and by a pair of upper longitudinalmembers each rigidly assembled at two junction nodes with one of saidlower longitudinal members so as to double same along a portioncorresponding to the cradle of the power unit, transmission andfront-wheel assembly by means of an upswept curved portion having anoutswept forward extension beyond said lower longitudinal members andtheir ends assembled by means of a curved horizontal cross member, saidlower longitudinal members having rear extensions, the second elementconsisting of an intermediate chassis member in the form of steelpressing formed in the conventional fashion with pressed reinforcingribs and constituting the floor of the passengers compartment andcomprising likewise pressed wells for the feet of the rear seatpassengers, and finally a third or rear element consisting of a pair ofparallel longitudinal members having a different relative spacing incomparison with said front longitudinal members.

According to another feature characterizing the body structure accordingto this invention one of the aforesaid junction or connecting points ornodes between said lower and upper longitudinal members pf the first orfront element of the chassis interconnects the top of each curvedportion of the upper longitudinal member and the front end of the lowerlongitudinal member, and further more said second junction pointssupport the main mountings of the power unit and of the thrust links ofthe driving front wheels.

On the other hand, a bow-shaped crossmember interconnects the two upperlongitudinal members of the front element of the chassis behind theengine and above the gearbox, this crossmember having upswept extensionsforming a relatively small angle with the vertical and adapted tosupport at their upper ends the bearing points of the front suspensionsystem.

This structure is characterized inter alia by the following advantageousfeatures:

By grouping, at very rigid junction nodes located at the front end, themain mounting points of the power unit and the mounting points of thefront-wheel thrust links, the vibrations produced by the power unit andfront wheel are mutually damped out at said junction nodes, the chassiselements lying at a neutral point of the transmission of saidvibrations, which is reinforced by the rubber pads provided at saidmounting points.

Similarly, the inherent flexion elasticity of the oblique builtinuprights bearing the springs and shock absorbers of the suspensionsystem coact with this system for damping out the vibrations caused byroad unevennesses and transmitted through the front wheels.

Finally, the type of discontinuous construction of the chassis structure(comprising relatively short longitudinal side members connectedseparately to a steel pressing in which very varied ribs and likereinforcing patterns are formed) provided by the present inventioncounteracts the generation and propagation of vibration frequenciesinherent to this structure.

The power unit and front wheel assembly or grouping necessitates thereinforcement of the chassis structure by doubling the longitudinal sidemembers only in this relatively limited zone. This leads to the use ofshorter and lighter longitudinal members that can be mass-produced onsmaller machines and tools.

it is one object of this invention to prevent this lighter structurefrom impairing the rigidity of the passengers compartment and thereforecompromise the passengers safety, while promoting the shock absorptioncapacity of the front portion of the vehicle.

Thus, in case of a front crash, the curvature of the front longitudinalside members and their horizontal end inclination will automatically fixits buckling point at its junction node with the lower longitudinalmember, thus directing the folding effect downwards, so as to dissipateone fraction of the shock energy by effecting a corresponding lifting ofthe nose portion of the vehicle and possibly causing the latter toclimb" the obstacle.

A stronger shock, after this initial buckling and the crushing of theradiator, will strike directly the power unit and possibly involve theyielding and eventually the shearing of its mountings; in this case, thepower unit will strike the bowshaped crossmember in the shoulder of itsrear portion. The backward torsion of this crossmember will absorb acomplementary fraction of the energy produced by the crash.

Under these conditions, it will be seen that due to this veryconsiderably shock-absorbing capacity the structure of the vehicleundergoes but a minimum distortion and that the passenger compartment,to which only moderate crushing forces are applied, since the heaviestmasses are concentrated at the front, remains substantially undamaged.

Other features characterizing this invention will appear as thefollowing description proceeds with reference to the accompanyingdrawing given by way of example and wherein:

FIG. 1 illustrates diagrammatically in elevational view the structure ofan automotive vehicle constructed according to this invention;

FIG. 2 illustrates the same structure but seen in plane view from above;

' lIl containing the main mountings of the power unit;

FIG. 4 illustrates the distortion of the front portion of the framestructure after the latter has absorbed a front shock,

FIG. 5 shows the configuration assumed by the frame structure and theengine position in case of a still stronger front shock.

Referring first to FIG. 1 showing in dash and dot lines 1 the externalcontour of the bodywork of the vehicle, the front frame structure,comprising a pair of upper longitudinal members 2 and a pair of lowerlongitudinal members 3, supports the power unit assembly comprising theradiator 4, the engine 5 and the transmission mechanism or gearbox 6,together with the front train of wheels including the wheels proper 7,of which the transmission, steering and braking mechanisms, not shown,are connected to the chassis through the suspension members 8, on theone hand, and thrust links 9, on the other hand.

The upper longitudinal side members 2 are interconnected at their frontoutswept portions 2, by a curved horizontal crossmember and behind theengine 5 by an arcuated or bow-shaped crossmember 11 overlying thetransmission mechanism or gearbox 6.

Each upper longitudinal side members 2 comprises a convex curved portion12 corresponding substantially to the zone surrounding the engine 5; thetop 13 of the curved. portion 12 constitutes the junction node whereatit is connected to the front end of the lower longitudinal member 3. Thelatter comprises a rear extension 3, behind the rear junction node 14,which lies under the floor-forming steel pressing 15 of the passengers'compartment, said extension 3 being rigidly connected to said steelpressing 15. The rear ends 3 of longitudinal side members 3 are weldedto the front wall of the wells 16 constituting the floor of the rearseats.

Similarly, the front ends 17 of the pair of rear longitudinal members 17are connected to the rear wall of said wells 16. The front portion 17 ofthese longitudinal members 17 extend under the floor sheet 15 and arewelded or otherwise fastened thereto. This sheet has formed therein agreat number of pressed ribs 15, for stiffening it and preventing thetransmis sion of undesired vibration. The longitudinal rigidity of thefloor portion of the passengers compartment is also reinforced bylongitudinal external or marginal side members 15 of known construction,for assembling the floor with the upper portion of the vehicle body 1.

The fuel tank 18 is fitted between the rear portions of the rearlongitudinal members 17; its flat and reinforced bottom 19 is level withthe upper edge of these longitudinal members and constitutes the floorof the boot.

The bearing points 20 of the suspension system 21 of the train of rearwheels 22 are supported by the intermediate portion of the rearlongitudinal members 17.

In FIG. 2 the arrangement of the half crossmembers 23, 24 supporting theanchor points 25 of the thrust links or arms 26 of the rear suspensionare clearly shown; these crossmembers are fastened to the rear edge ofthe floor pressing 15; another crossmember 30 disposed between the rearlongitudinal members 17 has pivotally mounted thereon a link 32connected to the rear axle; other crossmembers 31 and 33 complete theframing of tank 18; at the front and rear ends thereof. Sheets 34 alsowelded to the bodywork 1 form lateral extensions of the top of tank 18to constitute the boot floor.

The power unit and transmission mechanism assembly 5, 6 is connected tothe underframe at the junction nodes 13 by means of the central enginemountings 13 and at the other junction nodes 14 by means of the reargearbox mountings 14 these mountings being provided according to thewellknown technique with rubber blocks or like resilient means.

The thrust links 9 go through the junction tops 13; they are also, asknown in prior art, on the points 3, of the frame structure through themedium of the rubber blocks.

The front elevational view of the front train of wheel shown in FIG. 3illustrates the arrangement of the upper and lower wishbone or likesuspension links 8, of suspension system 8, the transmission shafts 27provided with universal joints for transmitting the drive to the frontwheels, as well as the oblique uprights 28 rigid with the upper frontlongitudinal members 2 and also with the arcuated crossmember 11, theseuprights 28 receiving at their upper ends 29 the bearing points of thesuspension elements 8.

FIG. 4 shows the front portion of the vehicle of FIG. 1; the dash lineillustrates the profile contour of the elements after the chassis fronthas struck an obstacle, with the consequent backward and upwarddisplacement of the power unit and gearbox assembly 5, 6 due to theabutment thereof against the arcuated crossmember l1 somewhat bentbackwards by the impact.

During the shock, the concentration of the reactions produced by themain engine mountings at nodal points 13 with the thrust or tractionreactions exerted by the front trains of wheels against the thrust links9 is such that it limits considerably the transmission of the possibleeffects of these ac tions, in the form of elastic distortion andvibration, to the chassis elements 2 and 3 lying in a substantiallyneutral position between these sources of mechanical strain andvibration. On the other hand, the inertia of the mass comprising thepower unit and transmission mechanism assembly tends in all cases tocounteract the action of the front driving wheels, thus causing a mutualcompensation of their reaction at said points 13.

The vertical reaction F of the suspension against the bearing orjunction point 29 (FIG. 3) is decomposed into two forces: F in thelongitudinal direction of upright 28, and F at right angles thereto. Incase of considerable stresses beyond the capacity of suspension 8, theinherent elasticity of upright 28 will assist in absorbing the componentF of these stresses, by a sinking flexion in relation to its junction tothe longitudinal member 2 and crossmember 11.

The positioning of the bearing points of the engine 5 at 13, that is, atthe top of the curved portion 12 of longitudinal members 2 is such thatthe engine mounting points are raised to the uppermost permissiblelevel, the bearing reactions converging to a point P of theoreticalanchoring (FIG. 3). This last-mentioned point lies well above the centerof gravity G of the power unit and provides a substantially pendularsuspension thereof.

Thus, in case of front crash, the energy thereof can be absorbed by thethrusting of the crossmember l0 and a torsion of the oblique ends 2, ofthe upper longitudinal members 2 without endangering the mechanicalcomponents of the vehicle.

A stronger shock will subsequently buckle the upper longitudinal members2 at points 13, the portion 2 being thus bent downwards so that thefront portion of the vehicle is raised accordingly. In the case ofimpact into an obstacle of relatively moderate height, this liftingeffect and the sledge shape of the front chassis element facilitates theclimbing of the obstacle and the corresponding absorption of the shock.

if a greater impact energy is applied to the front of the vehicle, itwill be absorbed by the engine 5 itself, after the radiator 4 has beencrushed, by bending and shearing the connecting members 13, and 14,. Thebackward shifting of the engine will cause it to strike the crossmember11 of which the torsion attended by the backward bending thereof willfurther absorb a considerable amount of energy.

The front portion of the vehicle will then have roughly theconfiguration shown in dash lines in FIG. 4, without casing anydistortion of the passengers compartment. This distortion will occuronly at a later stage, in case the front end were folded" about thejunction point 14 as shown diagrammatically in FlG. 5 wherein theoriginal shape of the vehicle is shown in dash lines. In this case thestructure according to this invention will permit of lifting the powerunit and gearbox assembly against the transverse member of the dashborador facia 30 by pivoting about the end of the gearbox 6 bearing on theground, thus absorbing an additional amount of energy before the powerunit eventually penetrates dangerously into the passengers compartment.

By way of example, a full-size front crash test carried out with avehicle having a chassis-body structure according to this invention,weighing 1,007 kilograms and driven at 30 mph. was attended by abackward thrust of 16.73 inches from the front to the wheel axis, theengine receding by 16.15 inches, while the body structure as contractedby 1.85 inches, the total contraction of the vehicle being 18.88 inches;finally, the appearance of the vehicle after the crash was substantiallyas shown in FIG. 5, thus proving the existence of additionalpossibilities of absorption by accentuating the bending and buckling ofthe longitudinal members 2 and 3 while tilting the engine against thebeam of the dashboard or facia 30.

Under these conditions it is clear that the chassis structure accordingto this invention is capable of giving to front-engined vehicles acapacity of absorbing front shocks at least equivalent to that hithertoobtained only with rear-engined vehicles.

Although a single from of embodiment of the invention has been shown anddescribed herein, it will readily occur to those conversant with the artthat various modifications may be brought thereto without departing fromthe spirit and scope of the invention as set forth in the appendedclaims.

What is claimed as new is:

1. Chassis-frame structure of automotive vehicle, notably of vehiclehaving a front power unit and transmission mechanism assembly, withdriving front wheels connected through thrust links to the chassisframe, characterized in that it comprises a compound chassis consistingof an assembly of three main elements, that is, a front elementconstituted by a pair of lower parallel longitudinal members upswept attheir front ends, and by a pair of upper longitudinal members eachrigidly assembled at two junction nodes with one of said lowerlongitudinal members so as to double same along a portion correspondingto the cradle of the power unit, transmission and front-wheel assemblyby means of an upswept curved portion having an outswept forwardextension beyond said lower longitudinal members and their endsassembled by means of a curved horizontal crossmembers, said lowerlongitudinal members having rear extensions, the second elementconsisting of an intermediate chassis member in the form of a steelpressing formed in the conventional fashion with pressed reinforcingribs and constituting the floor of the passenger's compartment andcomprising likewise pressed wells for the feet of the rear seatpassengers, and finally a third or rear element consisting of a pair ofparallel longitudinal members having a different relative spacing incomparison with said front longitudinal members.

2. Chassis-frame structure according to claim 1, wherein a first frontjunction node of said upper and lower longitudinal members of said frontchassis element interconnects the top of the curved portion of eachupper longitudinal member and the front end of the lower longitudinalmember, and furthermore said second junction point interconnects therear end of the upper longitudinal member and a portion of said lowerlongitudinal member which is located at the rear of the transmissionmechanism and extends to the rear.

3. Chassis-frame structure according to claim 1, wherein the rear endsof the upper longitudinal members and the rear extensions of the lowerlongitudinal members of the front element of the chassis are rigidlyconnected to the steel pressing constituting the intermediate chassiselement and the floor of the passengers compartment, said rear portionsof the lower longitudinal members extending under said pressing, theirrear ends being rigidly assembled with the front walls of said wellsformed in said pressing.

4. Chassis-frame structure according to claim 1, wherein the frontportions of the rear longitudinal members constituting said third orrear element extend under the steel pressing of said intermediateelement and the front ends of said rear longitudinal members are rigidlyassembled with the rear walls of sad wells formed in said pressing.

5. Chassis-frame structure according to claim 2, wherein the frontjunction nodes of the upper and lower front longitudinal members receiveon the one hand the main bearing points of the power unit andtransmission mechanism assembly, and on the other hand the anchoringpoints of the thrust links of the driving wheels, the other junctionnodes of the front longitudinal members receiving furthermore thesecondary bearing points of the power unit and transmission mechanismassembly.

6. Chassis-frame structure according to claim 1, wherein a bow-shapedcrossmember interconnects the pair of upper front longitudinal membersbehind the power unit and above the transmission mechanism, saidcrossmember having at its ends integral oblique extensions constitutingnearly vertical uprights receiving at their upper ends the bearingpoints of the front suspension elements.

7. Chassis-frame structure according to claim 1, wherein a fuel tankhaving a flat and reinforced top constitutes the floor of the boot andis rigidly fitted between said pair of rear longitudinal members.

1. Chassis-frame structure of automotive vehicle, notably of vehiclehaving a front power unit and transmission mechanism assembly, withdriving front wheels connected through thrust links to the chassisframe, characterized in that it comprises a compound chassis consistingof an assembly of three main elements, that is, a front elementconstituted by a pair of lower parallel longitudinal members upswept attheir front ends, and by a pair of upper longitudinal members eachrigidly assembled at two junction nodes with one of said lowerlongitudinal members so as to double same along a portion correspondingto the cradle of the power unit, transmission and front-wheel assemblyby means of an upswept curved portion having an outswept forwardextension beyond said lower longitudinal members and their endsassembled by means of a curved horizontal crossmembers, said lowerlongitudinal members having rear extensions, the second elementconsisting of an intermediate chassis member in the form of a steelpressing formed in the conventional fashion with pressed reinforcingribs and constituting the floor of the passenger''s compartment andcomprising likewise pressed wells for the feet of the rear seatpassengers, and finally a third or rear element consisting of a pair ofparallel longitudinal members having a different relative spacing incomparison with said front longitudinal members.
 2. Chassis-framestructure according to claim 1, wherein a first front junction node ofsaid upper and lower longitudinal members of said front chassis elementinterconnects the top of the curved portion of each upper longitudinalmember and the front end of the lower longitudinal member, andfurthermore said second junction point interconnects the rear end of theupper longitudinal member and a portion of said lower longitudinalmember which is located at the rear of the transmission mechanism andextends to the rear.
 3. Chassis-frame structure according to claim 1,wherein the rear ends of the upper longitudinal members and the rearextensions of the lower longitudinal members of the front element of thechassis are rigidly connected to the steel pressing constituting theintermediate chassis element and the floor of the passengers''compartment, said rear portions of the lower longitudinal membersextending under said pressing, their rear ends being rigidly assembledwith the front walls of said wells formed in said pressing. 4.Chassis-frame structure according to claim 1, wherein the front portionsof the rear longitudinal members constituting said third or rear elementextend under the steel pressing of said intermediate element and thefront ends of said rear longitudinal members are rigidly assembled withthe rear walls of sad wells formed in said pressing.
 5. Chassis-framestructure according to claim 2, wherein the front junction nodes of theupper and lower front longitudinal members receive on the one hand themain bearing points of the power unit and transmission mechanismassembly, and on the other hand the anchoring points of the thrust linksof the driving wheels, the other junction nodes of the frontlongitudinal members receiving furthermore the secondary bearing pointsof the power unit and transmission mechanism assembly.
 6. Chassis-framestructure according to claim 1, wherein a bow-shaped crossmemberinterconnects the pair of upper front longitudinal members behind thepower unit and above the transmission mechanism, said crossmember havingat its ends integral oblique extensions constituting nearly verticaluprights receiving at their upper ends the bearing points of the frontsuspension elements.
 7. Chassis-frame structure according to claim 1,wherein a fuel tank having a flat and reinforced top constitutes thefloor of the boot and is rigidly fitted between said pair of rearlongitudinal members.